Σχόλια 0

Το κείμενο του εγγράφου

Delay tolerant networks are characterized by the sporadic connectivity between theirnodes and therefore the lack

of stable end-to-end paths from source to destination. Since the

future node connections are mostly unknown in these networks,

opportunistic forwarding is usedto deliver messages. However,

making effective forwarding decisions using only the network

characteristics (i.e. average intermeeting time between nodes)

extracted from contact history is achallenging problem. Based

on the observations about human mobility traces and the findings

ofprevious work, we introduce a new metric calledconditional

intermeeting time, which computesthe average intermeeting time

betweentwo nodes relative to a meeting with a third node

usingonly the local knowledge of the past contacts. We then

look at the effects of the proposed metricon the shortest path

based routing designed for delay tolerant networks. We propose

ConditionalShortest Path Routing (CSPR) protocol that routes

the messages over conditional shortest pathsin which the cost

of links between nodes is defined by conditional intermeeting

times rather thanthe conventional intermeeting times. Through

trace-drivensimulations, we demonstrate thatCSPR achieves

higher delivery rate and lower end-to-end delay compared to the

shortest pathbased routing protocols that use the conventional

intermeeting time as the link metric.

INTRODUCTION:

Routing in delay tolerantnetworks (DTN) is a challenging problem because at any giventime instance, the probability that there is an end-to-end path from a source to a destination islow. Since the routing algorithms for conventional networks assume that the links between nodesare stable most of the time and do not fail frequently, they do not generally work in DTN’s.Therefore, the routing problem is still an active research area in DTN’s. Routing algorithms inDTN’s utilize a paradigm calledstore-carry-and-forward. When a node

receives a message fromone of its contacts, it stores the message in its buffer and carries the message until it encountersanother node which is at least as useful (in terms of the delivery) as itself. Then the message isforwarded to it based on this paradigm, several routing algorithms with different objectives (highdelivery rate etc.) and different routing techniques.

However, some of these algorithms used unrealistic assumptions, such as the existence oforacles which provide future contact timesof nodes. Yet, there are also many algorithms basedon realistic assumption of using only the contact history of nodes to route messagesopportunistically. Recent studies on routing problem in DTN’s have focused on the analysis ofreal mobility traces, vehicular etc., Different traces from various DTN environments areanalyzed and the extracted characteristics of the mobile objects are utilized on the design ofrouting algorithms for DTN’s. From the analysis of these traces performed in previous work, wehave made two key observations. First, rather than being memory less, the pair wise intermeetingtimes between the nodes usually follow a log-normal distribution. Therefore, future contacts ofnodes become dependent on the previous contacts. Second, the mobility of many real objects arenon-deterministic but cyclic.

Hence, in a cyclic MobiSpace, if two nodes were often in contact at a particular time inprevious cycles, then they will most likely be in contact at around the same time in the nextcycle. Toshow the benefits of the proposed metric, we adopted it for the shortest path basedrouting algorithms designed for DTN’s. We proposeconditional shortest path routing(CSPR)protocol in which average conditional intermeeting times are used as link costs rather thanstandard2 intermeeting times and the messages are routed over conditional shortest paths (CSP).We compare CSPR protocol with the existing shortest path (SP) based routing protocol throughreal trace-

driven simulations. The results demonstrate

that CSPR achieves higher delivery rateand lower end-to-end delay compared to the shortest path based routing protocols. This showshow well the conditional intermeeting time represents inter node link costs (in the context ofrouting) and helps making effective forwarding decisions while routing a message.We propose anew metric calledconditional intermeeting timethat measures the intermeeting time betweentwo nodes relative to a meeting with a third node using only the local knowledge of the pastcontacts. Such measure is particularly beneficial if the nodes move in a cyclic so-calledMobiSpace in which if two nodes contact frequently at particular time in previous cycles, theywill probably be in contact around the same time in the next cycle.

Shortest path routing protocols for DTN’s are based on the designs of routing protocolsfor traditional networks. Messages are forwarded through the shortest paths between source anddestination pairs according to the costs assigned to links between nodes.

Furthermore, thedynamic nature of DTN’s is also considered in these designs. Two common metrics used todefine the link costs are minimum expected delay (MED) and minimum estimated expecteddelay (MEED). They compute the expected waiting time plus the transmission delay betweeneach pair of nodes. However, while the former uses the future contact schedule, the latter usesonly observed contact history. Routing decisions can be made at three different points in an SPbased routing:i) at source,ii) at each hop, andiii) at each contact. In the first one (sourcerouting), SP of the message is decided at the source node and the message follows that path. Inthe second one (per-hop routing), when a message arrives at an intermediate node, the nodedeterminesthe next hop for the message towards the destination and the message waits for thatnode. Finally, in the third one (per-contact routing), the routing table is recomputed at eachcontact with other nodes and the forwarding decision is made accordingly. Inthese algorithms,utilization of recent information increases from the first to the last one so that better forwardingdecisions are made; however, more processing resources are used as the routing decision iscomputed more frequently.

SYSTEM ANALYSIS:

EXISTING SYSTEM:

Message delivery in sparse Mobile Ad hoc Networks (MANETs) is difficult due to thefact that the network graph is rarely (if ever) connected. A key challenge is to find a route thatcan provide good delivery performance and low end-to-end

delay in a disconnected networkgraph where nodes may move freely. Some bridge nodes are identified based on their centralitycharacteristics, i.e., on their capability to broker information exchange among otherwisedisconnected nodes. Due to the complexity of the centrality metrics in populated networks theconcept of ego networks is exploited where nodes are not required to exchange informationabout the entire network topology, but only locally available information is considered. ThenSimBet Routing is

proposed which exploits the exchange of pre-estimated "between’s' centralitymetrics and locally determined social "similarity' to the destination node. We present simulationsusing real trace data to demonstrate that SimBet Routing results in delivery performance close toEpidemic Routing but with significantly reduced overhead. Additionally, we show that SimBetRouting outperforms PRoPHET Routing, particularly when the sending and receiving nodeshave low connectivity.

PROPOSED SYSTEM:

We propose Conditional Shortest Path Routing (CSPR) protocol that routes the messagesover conditional shortest paths in which the cost of links between nodes is defined by conditionalintermeeting times rather than the conventional intermeeting times. Through trace-drivensimulations, we demonstrate that CSPR achieves higher delivery rate and lower end-to-end delaycompared to the shortest path based routing protocols that use the conventional intermeeting timeas the link metric.

Routing in delay tolerant networks (DTN) is a challenging problem because at any giventime instance, the probability that there is an end-to-end path from a source to a destination islow. Since the routing algorithms for conventional networks assume that the links between nodesare stable most of the time and do not fail frequently, they do not generally work in DTN’s.Therefore, the routing problem is still an active research area in DTN’s.

We introduced a new metric called conditional intermeeting time inspired by the resultsof the recent studies showing that nodes’ intermeeting times are not memory less and that motionpatterns of mobile nodes are frequently repetitive. Then, we looked at the effects of this metric

on

shortest path based routing in DTN’s. For this purpose,we updated the shortest path basedrouting algorithms using conditional intermeeting times and proposed to route the messages overconditional shortest paths. Finally, we ran simulations to evaluate the proposed algorithm anddemonstrated the superiority of CSPR protocol.

IMPLEMENTATION:

MODULE DESCRIPTION:

NETWORKING MODULE:

Client-server computing or networking is a distributed application architecture thatpartitions tasks or workloads between service providers (servers) and service requesters,calledclients. Often clients and servers operate over a computer network on separate hardware. Aserver machine is a high-performance host that is running one or more server programs whichshare its resources with clients. A client also shares any of itsresources; Clients therefore initiatecommunication sessions with servers which await (listen to) incoming requests.

MULTI HOP MODULE:

Analyze the load for a homogeneous multi-hop wireless network for the case of straightline routing in shortest path routing is frequently approximated to straight line routing in largemulti-hop wireless networks. Since geographical and geometric attributes of nodes and routesaffect the nodal load, we employ results from geometric probabilities to solve the problem.Based on our analytical results, we are able to show the precise relationship between the numberof nodes and the load at each node, and the geographical distribution of the relaying load overthe network for different scenarios. Interestingly, straight line routing itself can balance the relayload over the disk in certain cases.

CPSR (Conditional Shortest Path Routing):

We propose Conditional Shortest Path Routing (CSPR) protocol that routes themessages over conditional shortest paths in which the cost oflinks between nodes is defined byconditional intermeeting times rather than the conventional intermeeting times. Through trace-driven simulations, we demonstrate that CSPR achieves higher delivery rate and lower end-to-end delay compared to the shortest path based routing protocols that use the conventionalintermeeting time as the link metric.

Routing in delay tolerant networks (DTN) is a challenging problem because at any giventime instance, the probability that there is an end-to-end path from asource to a destination islow. Since the routing algorithms for conventional networks assume that the links between nodesare stable most of the time and do not fail frequently, they do not generally work in DTN’s.Therefore, the routing problem is stillan active research area in DTN’s.

We introduced a new metric called conditional intermeeting time inspired by the resultsof the recent studies showing that nodes’ intermeeting times are not memory less and that motionpatterns of mobile nodes are frequently repetitive. Then, we looked at the effects of this metricon shortest path based routing in DTN’s. For this purpose, we updated the shortest path basedrouting algorithms using conditional intermeeting times and proposed to route the messages overconditional shortest paths. Finally, we ran simulations to evaluate the proposed algorithm anddemonstrated the superiority of CSPR protocol.

SIMULATIONS RESULT:

To evaluate the performance of our algorithm, we have built a discrete event simulator inJava.

In this section, we describe the details of our simulations through which we compare theproposedConditional Shortest Path Routing(CSPR) algorithm with standardShortest PathRouting(SPR). To collect several routing statistics, we have generated traffic on the traces ofthese two data sets. For a simulation run, we generated 5000 messages from a random sourcenode to a random destination node at each seconds. We assume that the nodes have enoughbuffer space to store every message they receive, the bandwidth is high and the contact durations

of nodes are long enough to allow the exchange of all messages between nodes.

SYSTEM DESIGN:

Data Flow Diagrams (DFD):

The data flow diagram (DFD) is one of the most important modeling tools. It is used tomodelthe system components. These components are the system process, the data used by theprocess, an external entity that interacts with the system and the information flows in the system.

DFD shows how the information moves through the system and how it is modified by aseries of transformations. It is a graphical technique that depicts information flow and thetransformations that are applied as data moves from input to output.

DFD is also known as bubble chart. A DFD may be used to represent a system at anylevel of abstraction. DFD may be partitioned into levels that represent increasing informationflow and functional detail.

A level 0 DFD, also called as the context level diagram, represents the entire system as asingle module with input and output data indicated by incoming outgoing arrows respectively.Additional process and information flow paths are represented as the level 0 DFD is portioned toreveal more details. The context level diagram for the proposed system is shown in the fig.

A level 1 DFD, also called as top-level DFD, represent the system with major modulesand data stores. The other levels will show each module in the top-level DFD in more detailedfashion. The top-level and other level DFD s for the proposed systems are shown next.

To context a data flow diagram four basic symbols are used. They are given below.

Notation:

Source or destination of data:

External sources or destinations, which may be people or organizations or other entities.

Data Source:

Here the data referenced by aprocess is stored and retrieved.

Process:

People, procedures or devices that produce data. The physical component is not identified.

Data Flow:

Data moves in a specific direction from an origin to a destination. The data flow is a “packet” ofdata

Modeling Rules:

There are several common modeling rules when creating DFDs:

1.

All processes must have at least one data flow in and one data flow out.

2.

All processes should modify the incoming data, producing new forms of outgoing data.

3.

Each data store must be involved with at least one data flow.

4.

Each external entity must be involved with at least one data flow.

5.

A data flow must be attached to at least one process.

Context Level or level-0 Data Flow Diagram:

CPSR

Network

New node

Join Request

Address

Data Flow Diagram : Level 1

New node

Re

Organizer

CPSR

Resolver

Routing

System

Join

Request

Address

&

Routing

Table

Network paths

cache

Network Tree

Un addressed

Tree

CPSR Routing

Nodes

Nodes

Addresses

Data FlowDiagram:

Level 2

New node

Node

Position

Calculation

CPSR

Updater

Join

request

Initial tree

New

Position

New Tree

Network Tree

Data FlowDiagram: Level

3

Re

address

nodes

Update

CPSR

New node

Position

Network

Tree

New

Addresses

Re address

Network tree

New node

Address

Network tree

Address

Calculator

SYSTEM STUDY:

FEASIBILITY STUDY:

The feasibility of the project is analyzed in thisphase and business proposal is put forthwith a very general plan for the project and some cost estimates. During system analysis thefeasibility study of the proposed system is to be carried out. This is to ensure that the proposedsystem is not a burdento the company. For feasibility analysis, some understanding of the majorrequirements for the system is essential.

Three key considerations involved in the feasibility analysis are



ECONOMICAL FEASIBILITY



TECHNICAL FEASIBILITY



SOCIAL FEASIBILITY

ECONOMICAL FEASIBILITY:

This study is carried out to check the economic impact that the system will have onthe organization. The amount of fund that the company can pour into the research anddevelopment of the system is limited. Theexpenditures must be justified. Thus the developedsystem as well within the budget and this was achieved because most of the technologies usedare freely available. Only the customized products had to be purchased.

TECHNICAL FEASIBILITY:

This study is

carried out to check the technical feasibility, that is, the technicalrequirements of the system. Any system developed must not have a high demand on the availabletechnical resources. This will lead to high demands on the available technical resources.Thiswill lead to high demands being placed on the client. The developed system must have a modestrequirement, as only minimal or null changes are required for implementing this system.

SOCIAL FEASIBILITY:

The aspect of study is to check the level of acceptance of the system by the user. Thisincludes the process of training the user to use the system efficiently. The user must not feelthreatened by the system, instead must accept it as a necessity. The level of acceptance by theusers solely depends on the methods that are employed to educate the user about the system andto make him familiar with it. His level of confidence must be raised so that he is also able tomake some constructive criticism, which is welcomed, as he is the final user of the system.

SYSTEM TESTING:

The purpose of testing is to discover errors. Testing is the process of trying to discoverevery conceivable fault or weakness in a work product. It provides a way to check thefunctionality of components, sub assemblies, assemblies and/or a finished product It is theprocess of exercising software with the intent of ensuring that the Software system meets itsrequirements and user expectations and does not fail in an unacceptable manner. There arevarious types of test. Each test type addresses a specific testing requirement.

TYPES OF TESTS:

Unit testing:

Unit testing involves the design of test cases that validate that the internal program logic isfunctioning properly, and that program inputs produce valid outputs. All decision branches andinternal code flow should be validated. It is the testing of individual software units of theapplication .it is done after the completion of an individual unit before integration. This is astructural testing, that relies on knowledge of its construction and is invasive. Unit tests performbasic tests at component level and test a specific business process, application, and/or systemconfiguration. Unit tests ensure that each unique path of a business process performs accuratelyto the documented specifications and contains clearly defined inputs and expectedresults.

Integration testing:

Integration tests are designed to test integrated software components to determine if theyactually run as one program. Testing is event driven and is more concerned with the basicoutcome of screens or fields.

Integration tests demonstrate that although the components wereindividually satisfaction, as shown by successfully unit testing, the combination of components iscorrect and consistent. Integration testing is specifically aimed at exposing the problems

thatarise from the combination of components.

Functional test:

Functional tests provide systematic demonstrations that functions tested are available asspecified by the business and technical requirements, system documentation, and user manuals.

Functional testing is centered on the following items:

Valid Input

:

identified classes of valid input must be accepted.

Invalid Input

:

identified classes of invalid input must be rejected.

Functions

:

identified functions must be exercised.

Output

:

identified classes of application outputs must be exercised.

Systems/Procedures: interfacing systems or procedures must be invoked.

Organization and preparation of functional tests isfocused on requirements, keyfunctions, or special test cases. In addition, systematic coverage pertaining to identify Businessprocess flows; data fields, predefined processes, and successive processes must be considered fortesting. Before functional testing is complete, additional tests are identified and the effectivevalue of current tests is determined.

System Test:

System testing ensures that the entire integrated software system meets requirements. It tests aconfiguration to ensure known and

predictable results. An example of system testing is theconfiguration oriented system integration test. System testing is based on process descriptionsand flows, emphasizing pre-driven process links and integration points.

White Box Testing:

White Box Testing is a testing in which in which the software tester has knowledge of theinner workings, structure and language of the software, or at least its purpose. It is purpose. It isused to test areas that cannot be reached from a black box level.

Black Box Testing:

Black Box Testing is testing the software without any knowledge of the inner workings,structure or language of the module being tested. Black box tests, as most other kinds of tests,must be written from a definitive

source document, such as specification or requirementsdocument, such as specification or requirements document. It is a testing in which the softwareunder test is treated, as a black box .you cannot “see” into it. The test provides inputs andresponds to outputs without considering how the software works.

Unit Testing:

Unit testing is usually conducted as part of a combined code and unit test phase of thesoftware lifecycle, although it is not uncommon for coding and unit testing to be conducted astwo distinct phases.

Test strategy and approach

Field testing will be performed manually and functional tests will be written in detail.

Test objectives:



All field entries must work properly.



Pages must be activated from the identified link.



The entryscreen, messages and responses must not be delayed.

Features to be tested:



Verify that the entries are of the correct format



No duplicate entries should be allowed



All links should take the user to the correct page.

Integration Testing:

Software integration testing is the incremental integration testing of two or moreintegrated software components on a single platform to produce failures caused by interfacedefects.

The task of the integration test is to check that components or software applications,

The Java programming language is a high-level language that can be characterized by allof the following buzzwords:



Simple



Architecture neutral



Object oriented



Portable



Distributed



High performance



Interpreted



Multithreaded



Robust



Dynamic



Secure

With most programming languages, you either compile or interpret a program so that youcan run it on your computer. The Java programming language is unusual in that a program isboth compiled and interpreted. With the compiler, first you translate a program into anintermediate language calledJava byte codes

—the platform-independent codes interpreted bythe interpreter on the Java platform. The interpreter parses and runs each Java byte codeinstruction on the computer. Compilation happens just once; interpretation occurs each time theprogram is executed. The following figure illustrates how this works.

You can think of Java byte codes as the machine code instructions for theJava VirtualMachine

(Java VM). Every Java interpreter, whether it’s a development tool or a Web browserthat can run applets, is an implementation of the Java VM. Java byte codes help make “writeonce, run anywhere” possible. You can compile your program into byte codes on any platformthat has a Java compiler. The byte codes can then be run on any implementation of the Java VM.That means that as long as a computer has a Java VM, the same program written in the Javaprogramming language can run on Windows 2000, a Solaris workstation, or on an iMac.

The Java Platform

Aplatform

is the hardware or software environment in which a program runs. We’ve alreadymentioned some of the most popular platforms like Windows 2000, Linux, Solaris, and MacOS.Most platforms can be described as a combination of the operating system and hardware. TheJava platform differs from most other platforms in that it’s a software-only platform that runs ontop of other hardware-based platforms.

The Java platform has two components:



TheJava Virtual Machine

(Java VM)



TheJava Application Programming Interface

(Java API)

You’ve already been introduced to the Java VM. It’s the base for the Java platform and is portedonto various hardware-based platforms.

The Java API is a large collection of ready-made software components that provide many usefulcapabilities, such as graphical user interface (GUI) widgets. The Java API is grouped intolibraries of related classes and interfaces; these libraries are knownaspackages. The nextsection, What Can Java Technology Do? Highlights what functionality some of the packages inthe Java API provide.

The following figure depicts a program that’s running on the Java platform. As the figure shows,the Java API and the virtual machine insulate the program from the hardware.

Native code is code that after you compile it, the compiled code runs on a specific hardwareplatform. As a platform-independent environment, the Java platform can be a bit slower thannative code.However, smart compilers, well-tuned interpreters, and just-in-time byte codecompilers can bring performance close to that of native code without threatening portability.

What Can Java Technology Do?

The most common types of programs written in the Java programming language areapplets

andapplications. If you’ve surfed the Web, you’re probably already familiar withapplets. An applet is a program that adheres to certain conventions that allow it to run within aJava-enabled browser.

However, the Java programming language is not just for writing cute, entertaining appletsfor the Web. The general-purpose, high-level Java programming language is also a powerfulsoftware platform. Using the generous API, you can write many types of programs.

An application is a standalone program that runs directly on the Java platform. A specialkind of application known as aserver

serves and supports clients on a network. Examples ofservers are Web servers, proxy servers, mail servers, and print servers. Another specializedprogram is aservlet. A servlet can almost be thought of as an applet that runs on the server side.Java Servlets are a popular choice for building interactive web applications, replacing the use ofCGI scripts. Servlets are similar to applets in that they are runtime extensions of applications.Instead of working in browsers, though, servlets run within Java Web servers, configuring ortailoring the server.

How does the API support all these kinds of programs? It does so with packages of softwarecomponents that provides a wide range of functionality. Every full implementation of the Javaplatform gives you the following features:



The essentials: Objects, strings, threads, numbers, input and output, data structures,system properties,date and time, and so on.

The Java platform also has APIs for 2D and 3D graphics, accessibility, servers, collaboration,telephony, speech, animation, and more. The following figure depicts what is included in theJava 2 SDK.

How Will Java Technology Change My Life?

We can’t promise you fame, fortune, or even a job if you learn the Java programminglanguage. Still, it is likely to make your programs better and requires less effort than otherlanguages. We believe that Java technology will help you do the following:



Get started quickly: Although the Java programming language is a powerful object-oriented language, it’s easy to learn, especially for programmers already familiar with C or C++.

Develop programs more quickly: Your development time may be as much as twice asfast versus writing the same program in C++. Why? You write fewer lines of code and it is asimpler programming language than C++.



Avoid platform dependencies with 100% Pure Java: You can keep your programportable by avoiding the use of libraries written in other languages. The 100% Pure JavaTMProduct Certification Program has a repository of historical process manuals, white papers,brochures, and similar materials online.



Write once, run anywhere: Because 100% Pure Java programs are compiled intomachine-independent byte codes, they run consistently on any Java platform.



Distribute software more easily: You can upgrade applets easily from a central server.Applets take advantage of the feature of allowing new classes to be loaded “on the fly,” withoutrecompiling the entire program.

to interface with database systems, programmers had to useproprietary languages for each database they wanted to connect to. Now, ODBC has made thechoice of the database system almost irrelevant from a coding perspective, which is as it shouldbe. Application developers have much more important things to worry about than the syntax thatis needed to port their program from one database to another when business needs suddenlychange.

Through the ODBC Administrator in Control Panel, you can specify the particulardatabase that is associated with a data source that an ODBC application program is written touse. Think of an ODBC data source as a door with a name on it. Each door will lead you to aparticular database. For example, the data source named Sales Figures might be a SQL Serverdatabase, whereas the Accounts Payable data source could refer to an Access database. Thephysical database referred to by a data source can reside anywhere on the LAN.

The ODBC system files are not installed on your system by Windows 95. Rather, theyare installed when you setup a separate database application, such as SQL Server Client orVisual Basic 4.0. When the ODBC icon is installed in Control Panel, it uses a file calledODBCINST.DLL. It is also possible to administer your ODBC data sources through a stand-alone program called ODBCADM.EXE. There is a 16-bit and a 32-bit version of this programand each maintains a separate list of ODBC data sources.

From a programming perspective, the beauty of ODBC is that the application can bewritten to use the same set of function calls to interface with any data source, regardless of thedatabase vendor. The source code of the application doesn’t change whether it talks to Oracle orSQL Server. We only mention these two as anexample. There are ODBC drivers available forseveral dozen popular database systems. Even Excel spreadsheets and plain text files can beturned into data sources. The operating system uses the Registry information written by ODBCAdministrator to determine which low-level ODBC drivers are needed to talk to the data source(such as the interface to Oracle or SQL Server). The loading of the ODBC drivers is transparentto the ODBC application program. In a client/server environment, the ODBC API even handlesmany of the network issues for the application programmer.

The advantages of this scheme are so numerous that you are probably thinking there mustbe some catch. The only disadvantage of ODBC is that it isn’t as efficient as talking directly tothenative database interface. ODBC has had many detractors make the charge that it is too slow.Microsoft has always claimed that the critical factor in performance is the quality of the driversoftware that is used. In our humble opinion, this is true. The availability of good ODBC drivershas improved a great deal recently. And anyway, the criticism about performance is somewhatanalogous to those who said that compilers would never match the speed of pure assemblylanguage. Maybe not, but the compiler (or ODBC) gives you the opportunity to write cleanerprograms, which means you finish sooner. Meanwhile, computers get faster every year.

JDBC:

In an effort to set an independent database standard API for Java; Sun Microsystemsdeveloped Java Database Connectivity, or JDBC. JDBC offers a generic SQL database accessmechanism that provides a consistent interface to a variety of RDBMSs. This consistent interfaceis achieved through the use of “plug-in” database connectivity modules, ordrivers. If a databasevendor wishes to have JDBC support, he or she must provide the driver for each platform that thedatabase and Java run on.

To gain a wider acceptance of JDBC, Sun based JDBC’s framework on ODBC. As youdiscovered earlier in this chapter, ODBC has widespread support on a variety of platforms.Basing JDBC on ODBC will allow vendors to bring JDBC drivers to market much faster thandeveloping a completely new connectivity solution.

JDBC was announced in March of 1996. It was released for a 90 day public review that endedJune 8, 1996. Because of user input, the final JDBC v1.0 specification was released soon after.

The remainder of this section will cover enough information about JDBC for you to knowwhat it is about and how to use it effectively. This is by

no means a complete overview of JDBC.That would fill an entire book.

JDBC Goals:

Few software packages are designed without goals in mind. JDBC is one that, because ofits many goals, drove the development of the API. These goals, in conjunction with earlyreviewer feedback, have finalized the JDBC class library into a solid frameworkfor buildingdatabase applications in Java.

The goals that were set for JDBC are important. They will give you some insight as to whycertain classes and functionalities behave the way they do. The eight design goals for JDBC areas follows:

1.

SQL LevelAPI

The designers felt that their main goal was to define a SQL interface for Java. Althoughnot the lowest database interface level possible, it is at a low enough level for higher-level toolsand APIs to be created. Conversely, it is at a high enough level for application programmers touse it confidently. Attaining this goal allows for future tool vendors to “generate” JDBC codeand to hide many of JDBC’s complexities from the end user.

2.

SQL Conformance

SQL syntax varies as you move from database vendor to database vendor. In an effort tosupport a wide variety of vendors, JDBC will allow any query statement to be passed through itto the underlying database driver. This allows the connectivity module to handle non-standardfunctionality in a manner that is suitable for its users.

3.

JDBC must be implemental on top of common database interfaces

The JDBC SQL API must “sit” on top of other common SQL level APIs. This goalallows JDBC to use existing ODBC level drivers by the use of a softwareinterface. Thisinterface would translate JDBC calls to ODBC and vice versa.

4.

Provide a Java interface that is consistent with the rest of the Java system

Because of Java’s acceptance in the user community thus far, the designers feel that theyshould not stray from the current design of the core Java system.

5.

Keep it simple

This goal probably appears in all software design goal listings. JDBC is no exception.Sun felt that the design of JDBC should be very simple, allowing for only one method ofcompleting a task per mechanism. Allowing duplicate functionality only serves to confuse theusers of the API.

6.

Use strong, static typing wherever possible

Strong typing allows for more error checking to be done at compile time; also, less errorappear atruntime.

7.

Keep the common cases simple

Because more often than not, the usual SQL calls used by the programmer are simpleSELECT’s,INSERT’s,DELETE’s andUPDATE’s, these queries should be simple to performwith JDBC. However, more complex SQL statements should also be possible.

Finally we decided to proceed the implementation using Java

Networking.

And for dynamically updating the cache table we go for MS

Access

database.

Java ha two things: a programming language and a platform.

Java is a high-level programming language that is all of the following

Simple

Architecture-neutral

Object-oriented

Portable

Distributed

High-performance

Interpreted

multithreaded

Robust

Dynamic

Secure

Java isalso unusual in that each Java program is both compiled and interpreted.With a compile you translate a Java program into an intermediate language called Javabyte codes the platform-independent code instruction is passed and run on thecomputer.

Compilation happens just once; interpretation occurs each time the program is executed.The figure illustrates how this works.

You can think of Java byte codes as the machine code instructions for the JavaVirtual Machine (Java VM). Every Java interpreter, whether it’s a Java developmenttool or a Web browser that can run Java applets, is an implementation of the Java VM.The Java VM can also be implemented in hardware.

Java byte codes help make “write once, run anywhere” possible. You cancompile your Java program into byte codes on my platform that has a Java compiler.The byte codes can then

be run any implementation of the Java VM. For example, thesame Java program can run Windows NT, Solaris, and Macintosh.

Java

Program

Compilers

Interpreter

My Program

Networking TCP/IP stack:

The TCP/IP stack is shorter than the OSI one:

TCP is a connection-oriented protocol; UDP (UserDatagram Protocol) is a connectionlessprotocol.

IP datagram’s:

The IP layer provides a connectionless and unreliable delivery system. It considers eachdatagram independently of the others. Any association between datagram must be supplied bythe higher layers. The IP layer supplies a checksum that includes its own header. The headerincludes the source and destination addresses. The IP layer handles routing through an Internet. Itis also responsible for breaking up large datagram into smaller ones for transmission andreassembling them at the other end.

UDP:

UDP is also connectionless and unreliable. What it adds to IP is a checksum for thecontents of the datagram and port numbers. These are used to give a client/server model-

seelater.

TCP:

TCP supplies logic to give a reliable connection-oriented protocol above IP. It provides avirtual circuit that two processes can use to communicate.

Internet addresses

In order to use a service, you must be able to find it. The Internet uses an address scheme

formachines so that they can be located. The address is a 32 bit integer which gives the IP address.This encodes a network ID and more addressing. The network ID falls into various classesaccording to the size of the network address.

networks. Building 11 is currently on one subnetwork and uses 10-bit addressing, allowing 1024 different hosts.

Host address:

8 bits are finally used for host addresses within our subnet. This places a limit of 256 machinesthat can be on the subnet.

Total address:

The 32 bit address is usually written as 4 integers separated by dots.

Port addresses

A service exists on a host, and is identified by its port. This is a 16 bit number. To send amessage to a server, you send it to the port for that service of the host that it is running on. Thisis not location transparency! Certain of these ports are "well known".

Sockets:

A socket is a data structure maintained by the system to handle network connections. Asocket is created using the callsocket. It returns an integer that is like a file descriptor. In fact,under Windows, this handle can be used withRead File

andWrite File

functions.

#include <sys/types.h>

#include <sys/socket.h>

int

socket(int

family,int

type,int

protocol);

Here "family" will beAF_INET

for IP communications,protocol

will be zero, andtype

willdepend on whether TCP or UDP is used. Two processes wishing to communicate over a networkcreate a socket each. These are similar to two ends of a pipe-

but the actual pipe does not

yetexist.

JFree Chart:

JFreeChart is a free 100% Java chart library that makes it easy for developers to displayprofessional quality charts in their applications. JFreeChart's extensive feature set includes:

A consistent and well-documented API, supporting a wide range of chart types;

A flexible design that is easy to extend, and targets both server-side and client-side applications;

JFreeChart is "open source" or, more specifically,free software. It is distributed under theterms of theGNU Lesser General Public Licence

(LGPL), which permits use in proprietaryapplications.

1. Map Visualizations:

Charts showing values that relate to geographical areas. Some examples include: (a)population density in each state of the United States, (b) income per capita for each country inEurope, (c) life expectancy in each country of the world. The tasks in this

project include:Sourcing freely redistributable vector outlines for the countries of the world, states/provinces inparticular countries (USA in particular, but also other areas);

Implement a new (to JFreeChart) feature for interactive time series charts---

to display aseparate control that shows a small version of ALL the time series data, with a sliding "view"rectangle that allows you to select the subset of the time series data to display in the main chart.

3. Dashboards

There is currently a lot of interest in dashboard displays. Create a flexible dashboardmechanism that supports a subset of JFreeChart chart types (dials, pies, thermometers, bars, andlines/time series) that can be delivered easily via both Java Web Start and an applet.

4.Property Editors

The property editor mechanism in JFreeChart only handles a small subset of theproperties that can be set for charts. Extend (or reimplement) this mechanism to provide greaterend-user control over the appearance of the charts.

CONCLUSION:

In this paper, we introduced a new metric called conditional intermeeting time inspiredby the results of the recent studies showing that nodes’ intermeeting times are not memory lessand that motion patterns of mobile nodes are frequently repetitive. Then, we looked at the effectsof this metric on shortest path based routing in DTN’s. For this purpose, we updated the shortestpath based routing algorithms using conditional intermeeting times and proposed to route themessages over conditional shortest paths. Finally, we ran simulations to evaluate the proposedalgorithm and demonstrated the superiority of CSPR protocol. These results show that theconditional intermeeting time represents link cost better than the standard intermeeting time.Therefore, in CSPR, more effective paths with similar average hop counts are selected to routemessages. Consequently, higher delivery rates with lower end-to-end delays are achieved. InSPR and CSPR algorithms here, we used source-routing and let the messages follow the pathswhich are decided at the source nodes.